Wednesday, May 29, 2013

1305.6359 (Zahra Shaterzadeh-Yazdi et al.)

On Measuring Coherence in Coupled Dangling-Bond Dynamics    [PDF]

Zahra Shaterzadeh-Yazdi, Lucian Livadaru, Marco Taucer, Josh Mutus, Jason Pitters, Robert A. Wolkow, Barry C. Sanders
We devise a scheme to characterize tunneling of an excess electron shared by a pair of tunnel-coupled dangling-bonds on a silicon surface - effectively a two-level system. Theoretical estimates show that the tunneling should be highly coherent but too fast to be measured by any conventional techniques. Our approach is instead to measure the time-averaged charge distribution of our dangling-bond pair by a capacitively-coupled atomic force microscope tip in the presence of both a surface-parallel electrostatic potential bias between the two dangling bonds, and a tunable mid-infrared laser capable to induce Rabi oscillations in the system. With a non-resonant laser, the time-averaged charge distribution in the dangling bond pair is asymmetric as imposed by the bias. However, as the laser becomes resonant with the coherent electron tunneling in the biased pair the theory predicts that the time-averaged charge distribution becomes symmetric. This resonant symmetry effect should not only reveal the tunneling rate, but also the nature and rate of decoherence of single electron dynamics in our system.
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